Biomarkers that accurately reflect acute and/or past exposure to harmful agents are crucial in any study aiming to reduce the incidence of diseases resulting from environmental chemicals or other exposures. The biomarkers evaluated to date in biological fluids with relatively non-invasive access generally lack organ specificity and are not sensitive enough to detect mild damage and/or damage that occurred in the past In Phase I we employed a novel approach to identify unique biomarkers of acute exposure to toxicants in two rodent models. Following administration of toxicants in rat liver and lung damage models, we immunopurifed oxidized organ specific proteins from serum using mini prep affinity resins prepared with antibodies against three oxidized amino acids, chlorotyrosine, nitrotyrosine and methanionine sulfoxide. We then identified those proteins that were liver or lung specific by the proteomics approach of 2D gel separation, computerized and robotic spot picking, in-gel digests and MALDI/MS analysis. We succeeded in identifying several such damage biomarkers in serum derived from both lung and liver after administration of ozone and CCl4. Having demonstrated proof of concept in Phase I, in Phase II we propose to expand our studies to multiple organ systems, develop and validate highly specific sandwich immunoassays for oxidized protein biomarkers specific for various tissues, demonstrate proof of diagnostic concept and develop a prototype miniarray consisting of multiple organ specific oxidized protein biomarker ELISAs. Our long-term objective is to develop miniarrays of rat and human, organ-specific, damage assessment biomarkers. In a broad sense these arrays can serve the toxicology industry for both environmental agent exposure assessment and for drug development toxicology studies in animals and humans. In addition, they could be useful in clinical settings for the identification and monitoring of diseases in which diagnosis is difficult or equivocal.